Roots provide a valuable antiseptic, useful for bacterial infections of the mouth, throat, respiratory system, and skin. Native to the dry woodlands and prairies of North America, it prefers poor, dry soils, growing to 1m (3ft). and blooming in August and September with small yellowish flowers. Wild indigo contains a blue dyestuff similar to true indigo, Indigofera tinctoria, a native of India, and early settlers to North America used it as a clothing dye, hoping to undercut the much more expensive Indian product; however it never became as commercially popular and by the 1700s had fallen out of favour as a dye plant. It was much more successful as a medicinal, entering the US Pharmacopoeia (1831-42). Roots are a valuable antiseptic for infections of the mouth, throat, respiratory system, and the skin. It is currently being considered as a treatment for chronic fatigue syndrome, in combination with other herbs, for its purported immune stimulating properties.